最后，我实现了一个自定义udf，将bytearray转换为base64，然后通过standard将其应用于罪犯字段 res = FOREACH parsed GENERATE my.little.pony.udf.package.ByteArrayToByteArrayB64($0.raw); 自定义项定义：

package my.little.pony.udf.package;
import java.io.IOException;
import javax.xml.bind.DatatypeConverter;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.DataByteArray;

public class ByteArrayToByteArrayB64 extends EvalFunc<DataByteArray> {
    public DataByteArray exec(Tuple input) throws IOException {
        if (input == null || input.size() == 0)
        return null;
        try{
            if (input.size() < 1){
                throw new IOException("Input is of size:"+input.size());
            }       

            DataByteArray data = (DataByteArray)input.get(0);
            String convertedBase64 = DatatypeConverter.printBase64Binary(data.get()); 
            return new DataByteArray(convertedBase64.getBytes("UTF-8"));

        }catch (ClassCastException e){
             throw new IOException("Tuple element at is really of type:"+input.get(0).getClass().getName());
        }catch(Exception e){
             throw new IOException("Caught exception processing input row ", e);
         }
    }
}